1. Field of the Invention
This invention relates to a (CoFe)Zr/Nb/Ta/Hf based target material used for forming a thin film for electronic components, such as a soft magnetic underlayer mainly used in a perpendicular magnetic recording medium, and to a method for producing the (CoFe)Zr/Nb/Ta/Hf based target material.
2. Description of Related Art
The recent progress in the magnetic recording technology is remarkable, and the record densities of magnetic record media are being heightened for increasing capacities of drives. In the magnetic record media for the longitudinal magnetic recording systems currently used worldwide, however, an attempt to realize a high record density leads to refined record bits, which require a high coercivity to such an extent that recording cannot be made with the record bits. In view of this, a perpendicular magnetic recording system is under study as a means of solving these problems and improving the record densities.
Japanese Patent Laid-Open Publication No. 2005-320627 discloses a method for producing a Co alloy target material comprising 1 to 10 atomic % of Zr, 1 to 10 atomic % of Nb and/or Ta, and the balance consisting essentially of Co, with regard to a target material used for forming a thin film for electronic components, such as a soft magnetic underlayer in a perpendicular magnetic recording medium. In this method, a Co alloy is subjected to a rapid solidification process to produce an alloy powder, and then the alloy powder having a particle size of 500 μm or less is pressed and sintered.
However, a soft-magnetic target material as disclosed in Japanese Patent Laid-Open Publication No. 2005-320627 has a disadvantage that the sputtering efficiency is reduced by low-leakage magnetic flux in the magnetron sputtering process because its alloy composition typically results in a high magnetic permeability. In a typical method of producing such a CoZrTa/Nb/Hf based target material, powder which is produced by a gas atomizing technique is consolidated and shaped through a hot hydraulic pressing process at 800° C. to 1200° C.
Meanwhile, magnetron sputtering method is generally used for the preparation of the aforementioned soft magnetic films. This magnetron sputtering method is a method in which a magnet is disposed behind a target material to leak the magnetic flux onto a surface of the target material for converging plasma in the leaked magnetic flux region, enabling a high-speed coating. Since the magnetron sputtering method has a feature of leaking the magnetic flux on the sputtering surface of the target material, in the case where magnetic permeability of the target material itself is high, it is difficult to form, on the sputtering surface of the target material, the leaked magnetic flux necessary and sufficient for the magnetron sputtering method. In view of this, there has been a demand for reducing the magnetic permeability of the target material itself as much as possible.